Distinct formation history for deep mantle domains reflected in geochemical differences

Doucet, Dr. Luc1, Li, Pr. Zheng-Xian1, El Dien, Hamed Gamal1,2, Pourteau, Dr. Amaury1, Murphy, Pr. Brendan1,3, Collins, Pr. William1, Mattielli,Pr. Nadine4, Olierook,Dr. Hugo5,6, Spencer,Asso. Pr. Christopher 1,7, Mitchell, Asso. Pr. Ross8

1Earth Dynamics Research Group, TIGeR, School of Earth and Planetary Sciences, Curtin University, Perth WA 6845, Australia, Bentley, Australia, 2Geology Department, Faculty of Science, Tanta University, Tanta, Egypt, 3Department of Earth Sciences, St. Francis Xavier University, Antigonish, , Canada, 4Laboratoire G-Time, Université Libre de Bruxelles, Brussels, Belgium, 5Timescales of Mineral Systems, Centre for Exploration Targeting – Curtin Node, Curtin University, Bentley, Australia, 6John de Laeter Centre, Curtin University,, Bentley, Australia, 7Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Canada, 8State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China

The Earth’s mantle is currently divided into the African and Pacific domains, separated by the circum-Pacific subduction girdle and each domain features a large low shear-wave velocity provinces (LLSVPs) in the lower mantle. However, it remains controversial as to whether the LLSVPs have been stationary through time or dynamic, changing in response to changes in global subduction geometry. Here we compile radiogenic isotope data on plume-induced basalts from ocean islands and oceanic plateaus above the two LLSVPs which show distinct Pb, Nd and Sr isotopic compositions for the two mantle domains. The African domain shows enrichment by subducted continental material during the assembly and breakup of the supercontinent Pangaea, whereas no such feature is found in the Pacific domain. This deep-mantle geochemical dichotomy reflects the different evolutionary histories of the two domains during the Rodinia and Pangaea supercontinent cycles and thus supports a dynamic relationship between plate tectonics and deep mantle structures.


Biography

After a PhD in St Etienne, France (2012), Luc moved to Brussels to apply the “non-traditional” stable-isotope systematics on Archean igneous. After an academic career break, he joined Professor Li and the Earth Dynamics Research Group (Curtin University) to work on the present-day and past connections between Earth’s mantle, supercycles.

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